Hi,
    My 84 did exactly the same thing. I checked my temp 2 sensor and found
that it had about 60-70 ohms less resistance when fully warm then the specs
said it should have. I am not sure if this would screw it up or not. I ended
up screwing in the idle bypass screw about .5 turns it smoothed it right out.
            Hope this might help,
                                    Jeff s